Ethereum Classic (ETC) is a fork of Ethereum.
Wrong.
Or perhaps Ethereum is a fork of Ethereum Classic
True.
And it shouldn't depend on who you ask. It is a historic fact. Ethereum forked from Ethereum Classic by changing the consensus rules of the previous (original) chain. The original blockchain was renamed to Ethereum Classic. So the classic people are those who didn't fork, and decided to be consistent with the original chain rules.